This invention relates to a method for repairing pipes laid underground, such as gas pipes, in their buried state, from the inside, using resin.
Underground pipes, such as gas pipes, generally consist of a main supply pipe commonly known as the "mains" located under the road, with numerous distribution pipes branching off to supply individual users with commodities such as gas. The distribution pipes leading from the mains to general household users generally consist of relatively small diameter pipes, and due to their small wall thickness are susceptible to developing leaks due to corrosion in the course of aging and deterioration. On the other hand, for mains laid under roads, pipe in the form of cast iron tubes joined together by pipe joints is used, both pipe diameter and wall thickness being larger compared to the distribution pipes, and the risk of leaks due to corrosion being small. But the pipe joints are susceptible to developing leaks due to changes in mating conditions and formation of gaps caused by the weight of vehicles passing over the pipe, or by distortion of strata due to earthquakes.
In order to repair such leaks, and for preventive maintenance against such leaks, it has been proposed in recent years to repair the pipes from their inside while the pipes are left underground, the distribution pipes being repaired internally by forming a layer of resin lining, and the mains by filling the pipe joints with resin, to enhance their sealage.
The invention seeks to provide a method for repairing underground pipes, under which both the distribution pipes and the mains can be repaired in successive operations, and under which tests as to whether the repairings have been made properly can be made in the process, enabling repairing operations to be performed efficiently while confirming the adequacy of the work.